Preheat your oven to 375°F (190°C) and coat a 9x13-inch baking dish with non-stick spray.

Combine coarsely crushed pretzels, brown sugar, all-purpose flour, vanilla extract, and melted butter in a mixing bowl. Press the mixture into the baking dish, reserving ½ cup for topping.

Bake the crust for 10 minutes until slightly golden, then allow to cool completely.

In a medium saucepan, combine fresh blackberries, granulated sugar, lemon juice, and cornstarch. Cook over medium heat until the mixture thickens and bubbles, about 5-7 minutes. Remove from heat and cool slightly.

Beat cream cheese until fluffy, then gradually add powdered sugar and Cool Whip, mixing until smooth.

Spread the cream cheese mixture over the cooled crust, then spoon the blackberry topping over it evenly. Sprinkle remaining pretzel crumbs on top.

Cover with plastic wrap and refrigerate for at least 4 hours or overnight for best flavor.